There are two ways of producing a polytetrafluoroethylene dispersed concentrated liquid: one is chemical concentration, the other is vacuum concentration. Since the chemical concentration method will generate a large quantity of organic waste water, it is seldom used in the production process, so the vacuum concentration method is given priority at present.
The conventional vacuum concentration method is that a dispersed emulsion (mother liquid) is absorbed into a concentration kettle in the vacuum state, and then is heated by a jacket so that the emulsion is boiled at about 50° C. to evaporate the water inside the emulsion. Since the evaporated steam (steam of mother liquid) is entrained with a large quantity of products and emulsion, it is necessary to arrange a purifying system to separate the products and the emulsion, and finally the steam is further absorbed by the absorption tower. A currently common method for preparing polytetrafluoroethylene concentrated liquid is vacuum concentration, in order to prevent the polytetrafluoroethylene emulsion from demulsification at a high concentration. A large quantity of emulgators are added into the concentration kettle, which can easily form a lot of foam entrainment in the evaporation process, and it is inevitable for a part of the emulsion and emulgators to be carried into the steam absorption tower with evaporation of the steam, resulting in the absorbed liquid polluted, thus it has to be directly discharged without being further used as industrial water. A concentration kettle with an annual output of 180 tons of PTFE emulsion needs to consume hundreds of thousands of fresh water per year.
In order to save water resource and reduce cost, it is necessary to develop a technology for purifying mother liquid steam of polytetrafluoroethylene dispersion liquid, the water in the steam can be purified and used in circulations by means of equipment reforms and improvement on operational process, etc.